A turbomachine such as a steam turbine or a gas turbine generally includes a rotatable shaft that extends axially within an outer casing. Multiple rows of stationary vanes or nozzles extend radially inwardly from the outer casing. Adjacent rows of stationary vanes are axially separated by a row of rotor blades. The rotor blades are coupled to the shaft and extend radially outwardly therefrom towards the outer casing.
A shroud or seal assembly extends from an inner surface of the outer casing towards a radially outer tip of each rotor blade. In particular turbomachines, the seal assembly is rigidly fixed in position. An outer radial gap is defined between the tips of the rotor blades and a sealing material is disposed along a radially inner portion of the seal assembly. Generally, the outer radial gap is sufficiently sized to allow for thermal growth of the rotor blades as the turbomachine transitions between various operating modes and/or to reduce the potential for a tip strike against the seal assembly while reducing fluid flow through the outer radial gap.
Rotor seals may be attached to the rotor shaft and may extend radially outward therefrom towards a bottom portion of the stationary vanes. A seal assembly including a sealing material is disposed along the bottom portion of the stationary vanes. An inner radial gap is defined between the rotor seals and the bottom portion of the stationary vanes. Generally, the inner radial gap is sufficiently sized to allow for thermal growth of the rotor shaft and/or the stationary vanes as the turbomachine transitions between various thermal transitions while reducing fluid flow through the inner radial gap.
In operation, a working fluid such as combustion gases or pressurized steam is routed onto a pressure side of each rotor blade. Kinetic and/or thermal energy from the working fluid is transferred to the rotor blades which causes the shaft to rotate. Typically, a portion of the working fluid may leak through the outer radial gap, thereby potentially reducing overall turbine efficiency. In addition, a second working fluid such as a cooling media may be routed through and/or around the stationary vanes to provide cooling thereto. In order to efficiently cool the various components, leakage of the second working fluid between the tip of the rotor seal and the sealing material should be minimized. Therefore, an improved system for reducing flow leakage between static and rotating components of a turbine would be useful in the turbomachine industry.